Quantitative analysis of the oxidative metabolism in HXK2- and REG1-deletion mutants of Saccharomyces cerevisiae

Deletion mutants with either deletion of HXK2 and REG1 of the wild-type strain Saccharomyces cerevisiae CEN.PK113-7D were quant. analyzed for the impact on carbon catabolite repression and the short-term effect of the oxidative metab. Therefore, continuous cultures and transient expts. were performed, which were followed by high frequency online anal. of multiple compds.It could be demonstrated that either deletion of HXK2 or REG1 alleviated repression of respiratory functions in steady state conditions. The most striking consequence of less repression was a const. level of the oxidative capacity in function of diln. rate in the oxido-reductive growth regime, which led to much higher biomass yields at diln. rates higher than Dcrit. Both mutants developed higher max. oxidative capacity and consequently slightly higher crit. diln. rate during steady state cultures. This finding suggests that also the max. oxidative mitochondrial activity must be effected by carbon catabolite repression. The metabolic response to a sudden glucose excess, characterized by the instant availability of respiratory potential and the formation of ethanol, was not reduced by the deletion of HXK2 or REG1. However, the deletion mutants exerted a quicker adaptation of oxidative capacity to higher growth rates, which was attributed to the derepressed character of the deletion mutants. This relieved metabolic behavior led to a quicker return to oxidative catabolism after sudden glucose excess. This suggests that the short-term effect was not only dependent on the availability of the oxidative capacity, but also a consequence of metabolic coupling. [on SciFinder (R)]